Nitrogen oxides (NOx) contained in exhaust gas emitted from vehicles are restricted as primary air pollutants, and therefore, various researches has been conducted to reduce emission of NOx.
As one method to reduce such harmful exhaust gases, a vehicle is equipped with an exhaust gas recirculation (EGR) system. Generally, NOx is increased when the amount of air in an EGR mixer is high and combustion is good. Therefore, the EGR system mixes a portion (for example, 5% to 20%) of exhaust gas discharged from an engine back into the mixer to dilute the amount of oxygen in the mixer and obstruct combustion, thereby suppressing the occurrence of NOx.
Further the EGR system can improve fuel efficiency. For example, in general, pumping loss is reduced in a low speed/low load region and ignition timing based on a decrease in temperature of a combustion chamber is advanced in a medium/medium load region through the EGR system, and thus, fuel efficiency of a vehicle can be improved.
One example of the EGR system includes a low pressure exhaust gas recirculation (LP-EGR) device. The LP-EGR device recirculates exhaust gas that has passed through a turbine of a turbocharger to an intake passage at a front stage of a compressor.
In addition, the EGR system generally includes a cooler, Such that recirculated exhaust gas is cooled by the cooler and supplied to a combustion chamber.
The conventional EGR cooler includes a cooling structure installed inside a separate housing, and requires various components such as a nipple or the like for connecting a recirculation line through which a recirculating gas flows outside of the housing, and incurs an increased manufacturing cost of a vehicle due to an increase in a length of the recirculation line.
Further, since it is difficult to firmly fix the EGR cooler inside the vehicle, the EGR cooler housing wobbles while the vehicle is moving, causing excessive vibration.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention, and therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.